Two separate studies are proposed. The first is aimed at answering some of the questions remaining regarding the ventilatory response of human subjects to periods of exercise. Specifically, these include (1) determining the role of conditioning to the indicator signal for the beginning and ending of an exercise period, (2) determining the role of the learning process in predicting ventilatory levels for various work loads, and (3) determining the role of the peripheral chemoreceptors in the rapid ventilatory component. In addition, quantitation of the respiratory responses of a sufficient number of human subjects for the development and validation of models of respiratory control should prove to be useful. The secondy study is aimed at answering some of the questions pertaining to post-hyperventilation responses of awake man. Specifically, these include (1) the role of the peripheral chemoreceptors and (2) the effect of active respiratory drive during the hyperventilation period. In addition, quantitation of the respiratory responses of a sufficient number of human subjects for the development and validation of models of respiratory control should also prove to be useful.